Dry shaver



Oct. 5, 1943. w. L. MARTIN 2,331,274

DRY SHAVER Filed Nov. 14, 1941 WEND'ELL 1.. MAQT/N Arrow/E 45.

Patented gays, 1943" DRY SHAVER Wendell L. Martin, Shaker Heights, Ohio, assignor to The Martin Brothers Electric Company, Cleveland, Ohio, a corporation of Ohio Application November 14, 1941, Serial No. 419,159

9 Claims.

This invention relates to dry shavers and more particularly to an improved form of hair cutting element therefor.

In electric dry shaving devices it is usual and customary to provide a reciprocating cutter member which coacts with a slotted or perforated shear plate to cut off the hairs as the workin face of the shear plate is moved over the skin. To produce a satisfactorily close shave the shear plate must be pressed against the skin in such a manner that the hairs are extruded through apertures in the plate so that they may be cut off at or slightly below the skin surface. Numerous forms of shear plates or guards have been proposed and used to accomplish this purpose. The most common forms previously employed have comprised perforated or slotted plates of very thin metal. With these devices rapid shaving is not possible because a large part of the face engaging portion of the plate or guard must consist of solid portions in order to provide sufficient material with the exceedingly thin metal to give the necessary strength. The shear plate on one well known form of electric dry shaver is made upof parallel bars approximately .020" wide separated by slots .008" wide. The bars are approximately .002" or .003" thick throughout their entire length. It is apparent that a cutting head of this type is very fragile and must be passed frequently over a given portion of skin area in order to insure that the entire area has been covered by slot openings.

It is among the objects of the present invention to provide a shear plate for dry shavers or the like which will have a relatively great slot area as compared to prior devices whereby fast cutting action will be obtained by reducing the number of times the device must be passed over a given area to completely cover it. Other objects of my invention include: the provision of a shear plate for dry shavers having bars, the ends of which form effective combs for directing the hair into position to be cut by the reciprocating cutter; the provision of a shear plate which will permit the hair to be severed at or below the skin level without danger of cutting the skin; the provision of a transversely slotted shear plate having large slot openings for the admission of hair to be cut; the provision of a shear plate havingbars and slots, the teeth being extremely rugged while maintaining their efficiency as skin protecting and hair cutting elements; the provision of a shear plate for dry shavers which may readily be manufactured of high carbon steel or the like and which may be hardened and tempered to provide a long-lived, fast cutting unit; the provision of a shear plate which may be economically manufactured by relatively simple machining operations; and the provision of an improved method for making a shear plate for dry shavers or the like.

The above and other objects of my invention will appear from the following description of a preferred embodiment thereof, reference being had to the accompanying drawing in which,

Fig. l is a side elevation of a thin sheet metal blank for one of my shear plates.

Fig. 2 is a vertical cross sectional view of the blank shown in Fig. 1, taken on line 2-2 of Fig. 1.

Fig. 3 is a fragmentary plan view of one end of a partially completed shear plate, after the slots have been milled but before grinding.

Fig. 4 is a vertical cross sectional View taken on line 4-4 of Fig. 3.

Fig. 5 is a vertical cross sectional view taken on line 5-5 of Fig. 4.

Fig. 6 is a fragmentary plan view showing one end of the finisher shear plate.

Fig. 7 is a vertical cross sectional view through one of the slots in the shear plate and taken on line 1-1 of Fig. 6.

Fig. 8 is a fragmentary vertical cross sectional view taken on line 8-8 of Fig. 7.

Fig. 9 is a fragmentary prospective view of a finished shear plate showing an end portion and several bars.

Fig. 10 is an illustrated fragmentary plan view of a pair of my improved shear plates disposed side by side as they would preferably be arranged in an electric dry shaver and also illustrating reciprocating cutters which coact with the shear plates to sever the hairs.

Fig. 11 is a diagrammatic view illustrating a preferred procedure for cutting the slots which form the diamond shaped bars of my shear plate.

Fig. 12 is a fragmentary illustrative cross sectional view of the milling cutters for forming the slots in the shear plate.

It will be understood that all of the views of the drawing are greatly enlarged in order to facilitate an understanding of the shape and arrangement of the parts of my shear plate. In Fig. 1 a generally channel shaped blank from which the finished shear plate is formed is illustrated. This blank includes end portions 1 and 2 spaced apart by the working face portion 5. Intermediate the ends I and 2 of the shear plate the corners of the channel shaped blank are bent inwardly, as clearly seen at 3 and 4 in Fig. 2, to form longitudinally extending concave corrugations on each edge of the blank. It will also be noted that the outer surface of the working face 5 of the shear plate is slightly concave and this concave working face, which extends between the end portions I and 2, is disposed slightly below the level of the top surfaces 6 and I of the end portions l and 2, H

Referring again to Fig. 2, it will also be seen that the inner surface 8 of the intermediate and 1 of the end portions l and 2.

The form and arrangement of the bars and slots which make up my improved shear plate will perhaps best be understood if a preferred procedure for forming the shear plate is now plates of the type described having bars which are of uniform minimum center thickness. This is of importance as it is the minimum bar thickness which determines to a considerable extent the closeness of the shave which is obtainable.

As is wellillustrated in Figs. 7 and 9, each separate bar of the finished shear plate has its described. Referring to Fig. 11, a blank such as that illustrated in Figs. 1' and 2 is shown supported at an angle (12 as illustrated) and fed against a milling cutter which comprises a plurality of closely spaced cutters each having teeth which are V-shaped in cross-sectional contour as shown in Fig. 12. Preferably as many outters are provided as there are slots to be formed in the blank and by feeding the blank against the rotating cutters into the position shown in Fig. 11 a series of slots will be cut through the corner formed between one of the longitudinal corrugations 3 or 4 and the working face of the plate. After a out has been made on one side, the blank is reversed and again fed against the cutter, care being taken to insure that the cutters are exactly aligned with the previously out slots. After these angle cuts are completed the shear plate will appear as shown in Figs. 3, 4 and 5 with slots out inwardly from each longitudinal edge of the face 5. These slots cut all the way through the face 5 except at the center thereof, an unsevered web or rib portion ll remaining.

After the above described milling operation, the partially completed shear plate, which still possesses excellent strength and rigidity even in the partially formed bars because of the unsevered rib II, is preferably heat treated to obtain the desired hardness. Objectionable warping of the bars or other elements of the shear plate during the heat treating operation is effectively resisted by the connecting rib II and the other parts of the blank. Furthermore, the warping, if any, which occurs will be substantially the same in each shear plate and the die which forms the blanks may be shaped to form the blanks so that any warping or distortion which occurs during heat treating will tend to make the finished blanks of the desired shape.

After the blanks have been milled and heat treated the under-surface 8. of the working face portion is ground to provide a flat or plane cutter track portion as shown at I2 in Figs. 7 and 9. This grinding operation may be accomplished by moving a relatively narrow abrasive wheel longitudinally of the blank with the periphery of the wheel engaging the inner surface 8. The width of the flat under-surface i2 is preferably just slightly greater than the width of the cutter l8 and thus the depressed track forms a guide to hold the cutter bar it centered. By grinding the convex surface 8 down to a flat surface the connecting web or rib ii is completely ground away and the individual bars which make up the working face are spaced apart by slots which extend entirely across the face 5 of the shear plate.

After the inner surface 8 is ground flat 8.

smoothing cut may be made by passing a grinding wheel of the desired radius over the concave outer surface 5. This finished grinding of the outer surface will remove any burrs or rough edges which remain after the milling operation and makes possible the production of shear thinnest portion l3 disposed at its center and has its thickest portions H at the ends. Due to the angle at which the V-shaped milling cutters engage the blank (see Fig. 11) the bars, which are generally indicated at B in the drawing, are substantially diamond shaped in plan view, being widest at their center portions and narrowest at their ends. Thus, where the bars B are widest they are also thinnest and where they are narrowest they are also thickest. By this tooth form maximum strength at all points is obtained. As the bars are relatively narrow at their ends they are spaced proportionately far apart at the edges 'of the working face and the narrow bar ends along each side edge form combs which are effective to direct the hair into the slots between the bars. The perspective view, Fig. 9, clearly shows that my improved bar form provides relatively wide V-shaped openings ii at the entrances to the slots between the adjacent bars B. The corners I! of the bars are preferably rounded on a rather short radius so that they will closely engage the skin and direct the hair into the slots.

From the above description of the diamond shaped bars which form my shear plate, it will be seen that the slots between the bars flare outwardly towards each end from the center. These slots are preferably approximately .005" wide at the center and approximately .020" wide at their outer ends. The bars are preferably about .003" thick at the center portions i3 and approximately .005" thick at the portions a which are at the side edges of the flat track portion ii.

In Fig. 10 I have illustrated a pair of my shear plates arranged as they would be in a dual head electric shaver. By using two of my shear plates side by side with two reciprocating cutters, which are indicated at i8 and I 9 in Fig. 10, a very rapid acting shaving head is provided which need be passed over the skin only a minimum number of times in order to give a complete shave.

When the shear plate is pressed against the skin the comb-like ends I! of the bars T will engage the skin with the greatest pressure due to the concave form of the outer surface 5. These bars will direct hairs into the V-shaped openings of the solts between the bars. As explained before, these slots are widest at the ends and narrowest at the center while the bars are thickest at the ends and thinnest at the center. The wider the slot opening the more tendency there will be for the skin to bulge into the slot; however, as the bars are thickest at the points where the slots are widest, the skin will not bulge down below the inner surface ill of the shear plate and, thus, will not be in the path of the cutters l8 or [9. So, likewise, at the center of each slot the bars are very thin and, although the slots are narrow, the skin will bulge inwardly to a point substantially the same as that which occurs at the outer ends of the slots.

Due to the diamond shaped contour of the bars, hairs may effectively be cut at any point along the length of the side face of a tooth. The hairs do not need to pass into the narrow center portion of the slots to be cut as they will be sheared by the reciprocating cutters. which are known manner, at any point along the side edge of the bar. The tendency for the hairs to be bent and cut above the skin surface by the reciprocating cutter is largely eliminated and an extremely smooth, close and rapid shave is obtained without cutting or pulling of the skin.

The shape of the bars which form my shear plate makes the working portion of the plate entirely self-supporting and independent of support from the reciprocating cutter blade. The diamond bar shape is such that when two shear plate units are assembled into a single head as shown in Fig. 10, the effective cutting area is very nearly 100 per cent of the area covered by one pass of the shaver. I preferably use between 44 and 48 bars per inch of plate length although the number may be varied to suit varying conditions. By forming the concave corrugations 3 and 4 in the longitudinal comers of the shear plate efiective comb-like edges are formed and stiffness and rigidity is provided in the entire shear plate unit.

Although I have illustrated and described in considerable detail one embodiment of my improved shear plate and a preferred procedure for making same, it will be understood by those skilled in the art that numerous variations and modifications may be made in my improved dry shaver cutting element and in the described method of producing it without departing from the spirit of my invention. I do not, therefore, wish to .be limited to the exact forms thereof herein shown and described but claim as my invention all embodiments thereof coming within the scope of the appended claims.

I claim:

1. A shear plate of the type described having a series of spaced apart generally diamond shaped bars which are relatively wide and thin at their central portions and relatively narrow and thick at their end portions and which are concave on their outer skin engaging surfaces.

2. In a shear plate for dry shavers or the like. a skin-engaging portion comprising a plurality of spaced bars extending transversely of said plate, each bar being widest at the center and tapering toward each end and being thinnest at the wide center portion and thickest at the ends, said spaced bars forming slots extending across the entire face of said skin-engaging portion and flaring outwardly from the center to each end.

3. In a shear plate for dry shavers or the like, a skin engaging portion having a concave outer surface and a plane inner surface, said portion including a series of spaced bars extendingtransversely entirely across said shear plate and being widest at the center and tapering toward each end, whereby a series of slots extending entirely through and across said skin engaging portion are formed, each of said slots being narrowest at the center and widest at each end.

4. A shear plate of the type described including a skin engaging portion comprising a series of spaced bars of generally diamond shape, adjacent bars being closest together on the longitudinal center line of said skinengaging portion and said bars being thinner at their central portions than at the ends.

5. A shear plate of the type described including a skin engaging portion having a series of spaced apart bars, each bar of said series being widest at its center and tapering inwardly toward each end, each bar of said series being thinnest at its center and gradually becoming thicker provided with a plurality of spaced teeth in wellshear plate.

at its ends, and each bar of said series having downwardly and outwardly inclined side walls.

6. In a shear plate of the type described, a skin contacting working face and supporting walls on each side of said skin contacting face, concave corrugations at the junctions between said skin contacting face and said supporting walls, said skin contacting face having a fiat cutter engaging portion on its inner surface and being transversely concave on its outer surface and including a series of spaced bars forming a series of slots, said slots extending across between said corrugations and being wider at each of their ends than at their center portions, the end portions of said bars being relatively narrow at their outer skin engaging surfaces and relatively wide at their junction with the corrugations in said side walls.

7.'A shear plate for dry shavers or the like comprising a generally channel shaped one-piece thin metal member having side walls and a connectingv wall, said connecting wall having and portions and a shearing section depressed below the plane of said end portions, the outer surface of said shearing section being concave in transverse cross-section, the inner surface of said shearing section having a portion lying in a plane and out of alignment with the inner surface of said end portions, concave corrugations extending lengthwise of said shear plate at the junction between said side walls and said shearing section of said connecting wall, and a series of transverse slots extending entirely across said shearing section between said corrugations and entirely through said connecting wall, said slots being narrowestat the center and widest at each end and forming a series of spaced bars having narrow portions and wide center portions at each end, said bars being thinnest at their center portions and thickest at their end portions.

8. A shear plate for dry shavers or the like comprising a generally channel shaped one-piece thin metal member having side walls and a connecting wall, said connecting wall having end portions and a shearing section depressed below the plane of said end portions, the outer surface of said shearing section being concave in transverse cross-section, the inner surface of said shearing section having a portion lying in a plane and out of alignment with the inner surface of said end portions, concave corrugations extending lengthwise of said shear plate at the Junction between said side walls and said shearing section of said connecting wall, a series of transverse slots extending entirely across said shearing section between said corrugations and entirely through said connecting wall, said slots being narrowest at the center and widest at each end and forming a series of spaced bars having narrow portions at each end and wide center portions, said bars being thinnest at the center portions and thickest at their end portions, and a cutter adapted to engage said plane portion of the inner surface of said shearing section.

9. In a dry shaver or the like, a shear plate having a series of spaced generally diamond shaped bars extending transversely across said shear plate, said bars being widest and thinnest at their central portions and narrowest and thickest at their end portions and having concave outer. surfaces, and a cutter having spaced bars positioned to engage the inner surfaces of said I bars and to reciprocate longitudinally of said WENDEIL L. MARTIN shear plate. 

